Ignition timing means



Aug. 31, 1937. K. A. HARMON IGNITION TIMING MEANS Filed April 1o, 19:56 2 sheets-sheet 1 nu. Mw

' INVENToR wrfr/n/WM y BY ATTORNEYS Aug. 31, 193.7.` K. A. HARMON IGNITION /TIMING MEANS 2 SheetsrSheat 2 Filed April 10, 1936 Aknk A I A m SNUR ll Y I A .B EN. 'Ill .lllllrlC r a Llllll-E i 4 y Jpn-a cal.'

- and' disadyantageouslyaffects the vacuum control -'operationlf 1 Paiement@ 31,' 1937 p This invention relates lto improvements in ignition timing'lmeans for-internal combustion en-V gines. The invention is. particularly .useful'in 'connection, with 'automobile engines which need 5 to be suiiiciently exible in opera-tion .to adapt themselvesl to `wid e variations in speed and-load. 'Ihe conventional form of ignition-tining control ,for automobile engines now generally use'd` 1 utilizes` a centrifugal lgovernor-'a-ndl a vacuum taken from the' intake manifold at a location ad'- jacent the throttlevalve. Th Qentrifugal gov-1 ernor -adv'ances and retards' the time. of ignition in direct proportion to engine speed, within-the..

' .limits of its range'of action. Beyond acertain speed, the centrifugal elements are arrestedby -a stop which limits their action butu'p'to this point' the'spark is advancedsubstantially indirect proportion to engine speed. 'I'he vacuum isut'ilized conjoin-.tly tvith the goyernor1-for varying the timing of ignition. The .vacuum iscaused .to advVance or retard the' spark accordingto increase or decreasein the suction prevailing inthe intake passage. 4The .vacuum control, by itself., provides .variations lin 'timing injaccordance' with' variations in the density of the charge taken into the.

'engine' cylinders; As 'the'amount of the charge of fuelmixture takenintq a cylinder increases'by a wider opening` of Vthe 'throttle valve, the'cpm- -pressionfof the' vcharge in the` cylinderincreases charges of larger 'vo-lume :are taken into-the cyllset the increased rateof flarxiepropagationin the :denser charge.' However, the vacuum control. does. notoperate, alone. It acts jointly with the centritugal governor andthe two'. do not combine 'The spark advancei referred to, isjfor Alevel* road v conditions although .it-*would not'fully do so. 'Ihe governor-control 'isf needed to provide the spark advance for varyingloadsiunder a wide open throttle condition. `But 1t acts at all 'times under constant' speed (conditions -foi` 1e vel road control for-the ignition tiiningtvhich islargely Atosaidpassag'e.` mf- 'I'hejtwo'vacuum-operated means combineland enceto gradual retardation of the spark with in l creasing speeds to compensate'for mixtures of in- .creasing densityandthe resulting increasing rate and 'thusthe density of-'the 'charge increases.; ,As 4istvell known', the 'rate oi flame propagation, through. the fuel' mixture 'increases with its .'density,other'factors being equal.' Thus,as.the

'23"- i'nder, the ignitionzsparlshbmd-occur.later te oir-'.1 Y cure'd by the conventional control. describedl The Ventrifvacuum which functions as a meas- .uring .mean s forthe fuel suppliedtotheen- "cept at the extreme higlr speeds, fand-it coun`te`x j ,acts the-retardation secured-'byV the ^vacuum,',=- direct'pl'oportionto the fuel supplied as measured operation at .various constant 'I'he `vac by the vacuum at. the Ventuiji- 'The Sprkdf -S mini-control alone' would morenearly satisfythe .they D pended claims.

independent f eng-ine' speed; whichenables-.the

elimination of centrfug'ally-operated sparkcon'- trol vdevices with'thexma'ny troubles 4and disadvant'ages incident thereto; and which vdepends entirely on thel engine-produced suction existing'4 5.

;'in theintake passage 4of theenginef-utilizin'g the l"suction produced at twodifferent points-in said passage to secure. a 'tiniing control which has much better characteristics thantho'se obtainable lo `withtheconyentional control described.

lMore particularly, it is an object o f .theinvene tion to provide a timing control actuated 4jointly. by two vacuum-operated means,l one of.whic`h responds to the vacuum vexisting in the .intake passage of the vengimeat a point vadjacent the throttle'valve and the-other of which responds to 'thevacuum existing in saidpassage at or near.-

the venturi or the point at which fuel is` supplied A b y their joint action produce'a spark timing curve for constant speed,- level road operation withthe desired characteristics, particularly with refero'f name propagation.' A'Iflie vacuum'at the v'en.`

-turi does not, likethe governor, adversely affect- --the action of the vacuum at--the throttle. 4'I [t'does jtimes.- Rather, it acts beneficially at times', when -neededto supplement'thevacuum-atthethrottle andlenalile-'characteristics of spark timing to'be' r Y secured by-'J'oint action whicncould not be see not, like the governor, actatfthe samer-'ate at allcured by the independent action of either ors,e"

gine,.and' is utilized here for the additionalpur# `4pose of spark 'contro1 and itqprovides a timing .vance' is ndt directly proportional to engine speed as it'is'withthe centrifugal' gov'ernor.- Bu't aside .-'from" this advantage whichis important; it is o f great importance to be abierto witha f centrifugal governorvwhichrhas' been a source Aofinany troubls tothe trade. Y

These and other features of invention 'will best A appearfaslthe detailed description proceeds.and

ev particularly pointed outigthefapf' Y 'I'he invention will be disclosed with reference to the accompanying drawings, in which:

Fig. 1 is a 'diagrammatical view showing an ignition timing apparatus embodying the inven- 5 tion; and

Fig. 2'is a chart illustrative of the operation of the apparatus shown in Fig. l and of the spark-timing characteristics secured by use of such apparatus. Y l Referring to Fig. 1 of these drawings; 5 represents the intake passage in the pipe B through which the mixture of fuel and air is drawn into the engine cylinders to be ignited. Air is admitted to passage 5 at the end 1 and fuel is supplied l5 thereto at another point, as by the pipe 8 which leads from the fuel supply chamber 9 of the carburetor. In the intake passage 5 and located beyond the point at which fuel is admitted and in position to control the amount of the mixture of fuel and air supplied `to the engine cylinders, is the usual throttle valve I 0. A venturi I I is pro--V vided in passage 5 between the throttle valve and the air admission opening, and the fuel is usually drawn in as shown, at the throat or location of greatest constriction of the venturi.

'I'hese parts have been illustrated simply in conventional Aform because they are the usual adjuncts of an internal combustion engine and their use and purposes are well understood.

The timer, likewise, has been shown simply in conventional form since its construction and operation is well understood in the art. The timer includes a pair of contacts I2 and I3, the former being carried by an arm Il, pivoted at I5 tol a '35 member I6 and movable in radially inward direction by a spring I 'I. The contact I3 is xed to member I6. One of the contacts is insulated from member I6 in any suitable manner. The

contacts I2 and I2, which are moved into engage- 40 ment by spring II', are separated by a cam I8 mounted on'a shaft I9 forming a part of or driven from the internal combustion engine. This cam engages a rubbing block 20, fixed on. the breaker arm Il. The member I6 is mounted for angular adjustment relatively to cam I8 and its shaft I8.

By moving member I6 clockwise the time of ignition will be advanced and by moving it counterclockwise the time of ignition will be retarded.

For actuating the timer, I utilize the suction developed at two spaced locations in the intake passage 5, one adjacent the throttle valve and one adjacent the point of fuel admission. The best locations. I believe, are those shown, wherein the opening 2I is so located as to be closed by thethrottle valve when that valve is closed and wherein the opening 22 is located at the throat of the venturi. The suction produced at 2I is added to that produced at 22 and the two effects, combined, arel utilized through the intermediary of any suitable means to actuatethe timer, ad-

vancing it as the total suction increases and retarding it as the total suction decreases.

An exemplary form of such an intermediary means is shown in Fig. 1. Here two bellows are 'c5 mounted one within another on a suitably fixed support 22. The inner bellows 24 is connected by a pipe 25 to the opening 2I while-the outer bellows 2i is connected by a pipe 21 to the opening 22. Both bellows act on the same member 28 and this movable member carries a rod 29 which is suitably connected, as by the pin and slot connection sho to an varm 20 on the breaker lplate Il. The spring of the bellows may serve as the force working in opposition to the engine- 76 produced suction to move the breaker plate in a counterclockwise direction or a separate spring such as shown conventionally at 2| may be used for this purpose.

It is to be understood that the apparatus shown in Fig. 1 is merelly an exemplary form. It is an 5 illustrative example of one of many forms which may be used to carry out the invention andthe invention is not to be limited to the one specific form disclosed. Any means which will respond to the vacuum existing in the intake passage at the 10 locations described, and effect timing adjustments of the circuit breaker may be used, as desired. The two means need not necessarily act together on the breaker plate as shown. All that is necessary is to'producey an angular movement be-4 15 tween the cam and breaker lever and it is immaterial, insofar as this invention is concerned, which of these elements is shifted and, of course, it is equally feasible as is well known in the art to shift one element by one means and the other 20 elementby the other means.

The operation of the invention will be explained with reference to the diagram of Fig. 2. In this figure the curves drawn in full lines represent spark advance and are to be read with reference 25 to the left hand scale of ordinates (degrees of spark advanceat the engine). The curves drawn in broken lines represent vacuum and are to be read with reference to the right hand scale of ordinates (vacuum in inches of water) The ab- 30 scissae, the same for all curves, represent speed,- in this case translated into miles per hour of the automobile driven by the engine. I vThe curve A shows the various degrees of vacuum .which will A exist at the throttle opening 2| when the throttle 35 is set to maintain various constant speeds on a level road. The curve B shows the various degrees of vacuum which will exist 'at the Venturi opening 22 for various speeds under the same condition. 'I'he curves C and D represent the vacuum 40 which exists at the throttle opening 2I and the Venturi opening 22, respectively, under a wide open throttle condition. Curve E represents the spark advance produced as the resultfof the vacuum shown at C plus that shown at D. Curve F 45 represents thespark advance which would be produced if the vacuum represented at A were utilized alone, while curve G shows the actual spark advance which is eected as the direct result of the vacuum shown at A plus that shown at B. 50

The bellows 24 and 26 are of different cross sectional areas so that for the same degree of vacuum the larger bellowsV 26 will produce a larger degree of spark advance than the smaller'. As herein shown, their areas are in the ratio of 4% 55 to 1. 30 inches of vacuum at the venturi will produce a spark advance of 20 degrees while 260 inches oi vacuum will produce a spark advance of 40 degrees. The curve F is, of course, directly proportional to curve A. Curve G, however, is .o proportional to the sum of curve F and the spark advance produced by curve B. If the spark advance secured for various vspeeds by the vacuum plotted at B be added to curve A, the result will be curve G. Y For example, at a speed of 60 g5 miles per hour, there is about 12 inches of vacuum at the venturi under the condition shown by curve B. This degree of vacuum will produce eight degrees of spark advance and curve G at 'the 60 mile per hour point will be found spaced 70 vertically eight degrees above curve F at the 60 mile per hour point. In combining curve C and D to get the spark advance curve E for wide open throttle conditions, the influence of curve C is practicallylnegligible. For example, at a speed u' of 60 miles perfhounlthe vacuum shown 'by curve '.sult such as is shownby that. part of curve Gf C is about 15 inchesbut the spark advance resulting from this degree of vacuum is only about two degrees, while the 30inch vacuum shown for 5 the same speed by curve D produces-a-twenty degree spark advance..

f The spark: advance provided for levelrroad op" eration, asvshown by curve Gr,-I is much. better adaptedto' the needs of present day,.high com- I lpression', automobile engines thanthat produced by any of the'prior art methods` of which I- am aware. From speeds of from 25 miles per hour upward, it provides the gradualretard in time of ignition necessary. Over the usual driving range,

:say from 25 to 50 miles per hour, the retardation. f isat a substantially uniform rate. As the speed of thefengineincreases, the charges taken 'into the cyllndersbecome' greater jandgreater and thus the mixture taken into the cylinders is subjected l 20 4to more and more compressionland becomes more and more dense. The rate of llame propagation.

infthefmixture'fincreases with the speed and laterV f timing o f theignition is required vto'oiset these.

increases. The curve A gives ju'st this result.

'25 From 55 miles per. hour upward the rate of in.

crease of compression is not as great due to the *ditliculty in getting'- full charges' .into the. cylin- -dersg at the extreme high speeds andthe spark advance' curve G. is designed to take care of $0 this condition by a less /rapidrateof retardation.'

'I'his change;-thls 'flattening out of curve G beycnd vhe'so mile per .hour point-, isdue to the iniiue'nc'e o'f .the vacuum at vthe venturi. As shown by curve B, the influenceof Athe vacuum at the 83 venturi is practically negligibleup to aspeed of 45 'miles per hour. Itustarts. out almost horizontal and nearly.V coincident with thehorizontal' g base line offthe diagram and does not diverge toV any great extent from such lineI until 'a speed A? of 30- miles per hour is reached and then only to a slight degree. But'bey'ond the 45 mile per hour point it begins to curve upwardly at a'great'- ly increased rate and produces 4'an increasing .de-

gree of spark-advance at a time when thevacuum 45 at the throttle opening is causing a too rapid retardation of the spark. rIfhe effect of the vacl uum at the venturi 'atvhigh speeds ois to offset to someextent the eiectvof the vacuum at the throttle and give the result desired as 'shown by the 50 curve G. 'Ihe curve .B, it will be seen, is not directly proportional to speed; The speed effectv is evident only at the higher 'speeds in contradlstinction'to'the usual 'arrangement where vacnum atfthethrottle plus centrifugal control 55.used. In such case-,the centrifugal control pro'- vides a spark advance curvewhich is a straight linefrom zero to the point wherev the governor weights reachthe limit of their, movementvwlien Athe curve Abecomesa. horizontal line (at the ex- 60 treme high speedsi. Thus, thecentrifugal gov` ernor modies aV vacuum curve, such` as A, by

adding to-.it uniform increments at all points.

from 'zero tothe high speed at which it ceases to function, and lthereafter at the extreme high- 65 speeds vit has no additional eiect'.- Irl-this case the curve .A is .not substantially modied until a' speed oi' about 25 miles perhour is reached and the greatest lmodiiication occurs when the extreme high speeds are reached, at which time the 70 modification is needed. The governor therefore.. acts constantly upto a certain point-and its;

effect is to vgive an'advance in spark at the higher speeds where actually retardation .is needed. The centrifugal Igovernor working in eonjunction 75 with -a vacuum at the throttle 'cannot yield a recentrifugal governor.

which lies in the speed range between the mile The curve G, from 'zero to 25 miles per hour .gives a' rapidly. increasing spark advance.` -At idling speeds, .a large4 retard is effected due to perliour point and the extreme high speed limit.

th .closing o 'of the throttle opening 2| by the 'closing of the throttle. The most importantand .novel Ve'iec'ts are found in that partof curve Gbeyondthe 25 mile per hour point,

' Thespark advance curve E vfor wide-open..

throttle conditions provides `for an advance 'which increases as thev speed increases. It differs, however, fromthe advance obtained with a centrifuits action.

to 25 miles per hour) havinga much more gradual slope than the remaining portion. The result is a relatively small rate of spark advance for the engine. when working at 4low speeds underlieavy` loads.- and a more' rapid rate of spark advance v forthe higher speeds'and lighter loads. This -spark advance, as will be seen from, a comparison of curves Dand E is 'directly proportional tothe vacuum` at the venturi'and' not to speed. The amount-of vacuum at the venturi determines the amount of fuel supplied to the engine and thus the spark advance for varying load conditions under a, wide open throttle is made indirect proportion to the amount of'fuel supplied, which is considered a. logical solution of the problem and.

a better one than to vary the spark in direct proportion to speed as is 'I'heutilization 'of vacuum at the venturi as -.the means for securing the spark advance for wide open throttle conditions enables me to vdisvy pense entirely with Vthe centrifugal governor;

which has quite generally been'fused for this purpose.. centrifugal governor, when used usually done with the` 'rl-2e for ign ition ontrol of v.present day automobile engines, which have very highy compression,

.presnts many difficulties which -were not experienced in thel past. The` modernengineis much more sensitive to timing'. In many casesfa spark advance as low as 10 degrees is used and slight variations in the action of the governor, which variations would not -be noticeable with the large .spark advances such as 30 to 45' degrees, 'formerly used, will materially affect the engine performance. Any looseness or play in the governor.

is taken up at the circuit breaker and causes vari-- ations in timing. For example, referring to Fig. l whenthe cam IB engages member- 20 to move the breaker arm' outwardly, 'there is a tendency for the'carn to be held back until any lost motion in 'the governor .is taken up, with .the result that there will be aslight retarding of the timingby delay in opening the breaker. points. Subsequently as the breaker arm moves inwardly, there will be a tendency for the cam' to move rapidly ahead and cause 'a' premature closing` of the points.

'I'hese tendencies .will Vresult in a. pulsating actionof the circuit breaker if lost motion is prese t,

the governor not being able. to hold the cam within close limits ,in lts intended position with reference to tl`ie..sha.ft. Space limitationsl pre- .clude an increase in size of the governor 'to an extent such as to definitely Stop this trouble.

whereas' with the arrangement disclosed. the bel' lows may be made large enough to supply a large .enough force to hold th adjustable element of the timer against such pulsating movements. The

of speed, cannot be adequately served by the governor. If its weights are so made as to give the necessary power to start at low speeds, they move 5 outwardly too fast at high speeds and are dimcult to control. If they are made properly for the higher speeds, they fail to start at the lower speeds and, at best, all that can be obtained is a rough approximation of the results needed. These governors are susceptible to wear and the wear results in play and causes variations vin timing. With the Venturi vacuum utilized as disclosed, the mechanical troubles heretofore experienced with the governor, its tendency to pulsating l5 action and variations in timing are, eliminated and a much better spark advance for wide open throttle conditions is obtained and vone which is not likely to get out of order and which is not susceptible to rapid wear with resulting inaccuracies in timing.

It will be understood that the gures, referred to herein for speed, vacuum and spark advance, havebeen given by way of illustrative example and that they are not intended to be used as setting up limitations. The chart of Fig. 2 shows the' results of one typical case where the invention has been applied to a well known make of automobile. a In this case, it was arbitrarily decided that a spark advance of 40 degrees was desired at a speed of 25 miles per hour for the condition of constant speed operation on'level road and that a spark advance of 20 degrees was desired at a speed of 60 miles per hour under the condition of a wide open throttle. The vacuum prevailing at these speeds, under these conditions,v

was made by the mechanism disclosed to eiect the amount of spark advance named. Obviously, other figures for speed Yand spark advance could have been chosen as starting points. Also, the range of speeds, the amount of vacuum and the degrees of spark advance may vary within wide limits. However, the one specic example given is a typical one and fully illustrates the performance obtained by the use of the invention when. applied to automobile engines of the present day type.

'Ihe invention thus provides an improved ignition timing means, characterized in that the vacuum at two vpoints in vthe engine intake is utilized to secure by joint action a spark advance for constant speed, level road conditions having characteristics adapted for the modern automobile engine and in that a better spark advance is secured for wide-open throttle conditions by the utilization of the vacuum at one or both of these points, than can be secured with the centrifugal governor.

What I claim is: v

1. An ignition timing control for internal combustion engines, wherein air and fuel are admitted into an intake passage at spaced points and the mixture of air and fuel is drawn into the engine cylinders under reduced pressure to be igmodern engine/with its greatly increased rangenited and wherein said passage is provided with a throttle valve to control the amount of the mixture drawn into said cylinders, comprising, a circuit breaker, a cam for operating the breaker, and means for ei'ecting a relative angular adjustment between the cam and breaker, said means responsive to the combined effect of the engineproduced suction in said passage at spaced points therein, one adjacent said throttle valve inA position to be closed by the throttle valve when closed and one adjacent Ythe point of admission of fuel.

2. An ignition timing control for internal combustion engines, wherein air and fuel are admitted into an intake passage at spaced points and the mixture "of air and fuel is drawn into the engine cylinders under reduced pressure to be ignited and wherein said passageis provided with a throttle valve to control the amount of the mixture drawn 'into said cylinders and with a venturi at the location where fuel is admitted, comprising, a circuit breaker, a cam for operating the breaker, and means for effecting a relative angular adjustment between the cam and breaker, said means responsive to the combined eect of the engine-produced suction in said passage at spaced points therein, one adjacent said throttle valve in position to be eclosed by the throttle valve when closed and one at the throat of said venturi.

3. In an internal combustion engine, having an intake passage provided with a venturi and a throttle valve, ignition timing means, a device actuated by iluid pressure and having a conduit connection with said intake passage opening into the latter at a point such that said connection will be closed by the closing of the throttle valve, a device actuated by fluid pressure and having a conduit connection with said intake passage opening into the latter at the throat of said venturi, and means connecting said devices to said timing meansto operate the latter by the combined effects of both devices.

a 4. In an internal combustion engine, having an intake passage provided `with an air admission opening, a throttle valve and. a venturi located. between said valve and opening, an ignition timing means, and operating means for the timing means comprising a device subjected to and movable responsive to a suction in said passage at a point adjacent said throttle valve and having a conduit l connection with said intake passage opening into the latter at a point such that said connection will be closed by the closing of the throttle valve, a device subjected to and movable responsive to the suction in said passage at the throat of said venturi, and connections between said devices and timing means for summing up the movements of said devices and operating the timing means proportionately to the sum of such movements, advancing the timing means as total suction increases and retarding it as the total suction decreases.

KENNETH A. HARMON. 

